Semiconductor high-power elements, including gallium nitride field-effect transistors (GaN FETs), have been increasingly used as power amplifying elements. Advantageous characteristics of the elements, such as long life, help promote the adoption of semiconductor amplifier elements also in amplifiers that used to be configured with vacuum-tube devices. However, the semiconductor amplifier elements alone produce smaller output power than the vacuum-tube devices, and thus the power amplifiers with the semiconductor amplifier elements may divide power of input signals among amplifier elements for amplifying the divided power and then combine the amplified power.
For example, Patent Literature 1 presents a power amplifying device having amplifiers connected in parallel. In the power amplifying device of Patent Literature 1, radial waveguides, which are a power divider and a power combiner, each have a height that is sufficiently smaller than a wavelength of a transverse electromagnetic (TEM) wave propagating through the waveguide. The power divider and the power combiner oppose each other with a slot planar antenna provided with slots on one side of each of the power divider and the power combiner. Amplifiers are inserted between the mutually opposing power divider and power combiner.
Patent Literature 2 discloses a high-frequency module designed to provide shielding performance for each element. The high-frequency module of Patent Literature 2 includes a dielectric substrate and a conductor cover. The dielectric substrate includes on a surface thereof a high-frequency circuit component including elements, a power source for supplying current to the high-frequency circuit component, and a control circuit component for controlling the high-frequency circuit component. The dielectric substrate further includes on both the surfaces thereof printed ground conductors electrically connected via through-holes of the dielectric substrate. The conductor cover includes upstanding walls located between the elements of the high-frequency circuit component and electrically connected to the ground conductors printed on the surfaces of the dielectric substrate. The upstanding walls form a separate enclosed space for each element.